Electrostatic couplings in OmpA ion-channel gating suggest a mechanism for pore opening
Electrostatic couplings in OmpA ion-channel gating suggest a mechanism for pore opening
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DOI：
10.1038/nchembio827
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发表时间：
2006-11-01
影响因子：
14.8
通讯作者：
Tamm, Lukas K.
中科院分区：
文献类型：
--
作者：
Hong, Heedeok;Szabo, Gabor;Tamm, Lukas K.
驱动通道和转运蛋白的开放和关闭状态之间结构转变的分子力尚不清楚。 OmpA 通道的栅极由中心 Glu52-Arg138 盐桥形成，该盐桥可以打开与 Lys82 和 Glu128 形成交替离子对。为了更深入地了解通道开放机制，我们通过双突变体循环分析测量了相关侧链之间的相互作用能量，并将其与相应点突变体的通道活性相关联。闭合的中心盐桥具有-5.6 kcal mol(-1)的强相互作用能，可以通过形成开放态盐桥Glu52-Lys82 (Delta Delta G(Inter) -3.5 kcal mol(-1))以及Arg138和Glu128之间的弱相互作用(Delta Delta G(Inter) = -0.6 kcal mol(-1))来打破。取代中心盐桥的共价二硫键完全阻断了通道。生长测定表明，这种门控机制在生理上有助于保护大肠杆菌细胞免受环境应激。
The molecular forces that drive structural transitions between the open and closed states of channels and transporters are not well understood. The gate of the OmpA channel is formed by the central Glu52-Arg138 salt bridge, which can open to form alternate ion pairs with Lys82 and Glu128. To gain deeper insight into the channel-opening mechanism, we measured interaction energies between the relevant side chains by double-mutant cycle analysis and correlated these with the channel activities of corresponding point mutants. The closed central salt bridge has a strong interaction energy of -5.6 kcal mol(-1), which can be broken by forming the open-state salt bridge Glu52-Lys82 (Delta Delta G(Inter) -3.5 kcal mol(-1)) and a weak interaction between Arg138 and Glu128 (Delta Delta G(Inter) = -0.6 kcal mol(-1)). A covalent disulfide bond in place of the central salt bridge completely blocks the channel. Growth assays indicate that this gating mechanism could physiologically contribute to the osmoprotection of Escherichia coli cells from environmental stress.